Shoal detection system

ABSTRACT

A mercury switch ideally suited for use in a shoal detector system has a vertically oriented cylindrically shaped capsule in which a quantity of mercury is retained and first and second electrodes, each having a ring-shaped contact portion disposed at opposite ends of the capsule so that when the capsule is vertically oriented the mercury will make contact with only one of the electrodes but upon angular displacement of the capsule in any direction, the mercury will contact both electrodes to close the switch. In one embodiment of the switch, a third electrode in the form of a straight conductive wire penetrates the mercury when the envelope is vertically oriented to provide means for testing an alarm circuit connected to the switch before the capsule is angularly displaced.

United States Patent 11 1 Fohey 1 Jan.7, 1975 SHOAL DETECTION SYSTEM [76] Inventor: Gerald J. Fohey, 3101 S. Norfolk,

Aurora, Colo. 80013 [22] Filed: Sept. 17, 1973 21 Appl. No.: 397,896

[52] US. Cl. 200/223, 200/235 [51] Int. Cl. 01h 29/00 [58] Field of Search 200/52 A, 6147, 220, 223,

ZOO/DIG. 8, 235

[56] References Cited UNITED STATES PATENTS 2,507,986 5/1960 Liss 200/220 3,198,919 8/1965 Tettke, Sr. et a1 200/235 3,356,812 12/1967 Moschetta, et al ..200/6l.47

Primary Examiner-Herman Hohauser Attorney, Agent, or Firm Burton, CrandeII & Polumbus [57] ABSTRACT A mercury switch ideally suited for use in a shoal detector system has a vertically oriented cylindrically shaped capsule in which a quantity of mercury is retained and first and second electrodes, each having a ring-shaped contact portion disposed at opposite ends of the capsule so that when the capsule is vertically oriented the mercury will make contact with only one of the electrodes but upon angular displacement of the capsule in any direction, the mercury will contact both electrodes to close the switch. In one embodiment of the switch, a third electrode in the form of a straight conductive wire penetrates the mercury when the envelope is vertically oriented to provide means for testing an alarm circuit connected to the switch before the capsule is angularly displaced.

2 Claims, 8 Drawing Figures Patented Jan. 7,1975 3,859,490

SI-IOAL DETECTION SYSTEM The present invention generally relates to mercury switch devices and particularly to a mercury switch device which is well suited for use in a shoal detector system.

When a boat is drifting or anchored in relatively shallow waters, it is desirable to have a shoal detector system for warning the operator of the boat when the water becomes too shallow for navigation. Typical shoal detector systems have a normally vertically oriented detecting member with a mercury-type switch therein suspended by a cable or the like from the boat so that when the switch drags on the bottom of the body of water, the switch is displaced from its normal vertical orientation to set off an alarm, warning the operator of the boat of the shallow water conditions.

It is an object of the present invention to provide a shoal detector system utilizing a new and improved mercury switch adapted to close an alarm circuit when tilted in any direction from its normal vertical orientation.

It is another object of the present invention to provide a new and improved mercury switch device including an enclosed capsule having a pair of electrodes with ring-like contact portions disposed at opposite ends of the capsule and a quantity of mercury normally engaging only one of the electrodes but adapted upon displacement of the device from its normal vertical orientation to engage both electrodes to close the switch.

It is still another object of the present invention to provide a new and improved mercury switch device having an enclosed capsule with first and second electrodes disposed therein having ring-like contact portions at opposite ends of the capsule with a quantity of mercury in the capsule engaging only one of the contacts when the capsule is vertically oriented and adapted to engage both contacts when the capsule is displaced from its vertical orientation, and further including a central axially extending electrode in engagement with the mercury in the vertically oriented position to establish means for testing a circuit connected to the switch.

These and other objects of the present invention are obtained with a new and improved mercury switch which may be incorporated into a shoal detector system to reliably detect shallow water conditions when the switch is angularly displaced in any direction. More particularly, the mercury switch device of the present invention includes an enclosed vertically orientated capsule having a first electrode with a ring-like contact portion disposed adjacent the bottom of the capsule and a second electrode with a ring-like contact portion adjacent the top of the capsule whereby a quantity of liquid current conducting material retained in the capsule at a level between the ring-like portions of the electrodes will engage only the lower electrode when the switch is disposed in its normal vertical orientation, but when the capsule is tilted in any direction at an angle to vertical, the liquid material will flow into contact with both the upper and lower electrodes closing the switch.

In an alternative embodiment of the switch which enables an electrical circuit connected to the switch to be tested without tilting the capsule, a third electrode extends along the central axis of the capsule and projects into the liquid material when the capsule is vertically oriented so that the circuit can be closed without tilting the capsule. This provides a convenient means for making sure that a power source and alarm means in a shoal detection system or the like are functioning properly without having to tilt the switch capsule.

As will be more appreciated with the detailed description hereinafter, when the mercury switch of the present invention is incorporated into an alarm circuit and mounted in a detector device suspended by a cable means or the like from a boat so as to normally occupy a vertical orientation, and the detector device engages the bottom of a body of water causing it to tilt from vertical, the ring-shaped contact portions of the electrodes will become simultaneously engaged with the liquid material to close the switch and close the alarm circuit.

Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view of the shoal detector system of the present invention suspended from a boat;

FIG. 2 is an enlarged fragmentary side elevational view showing the weighted shoal detector element dragging on the bottom surface of a body of water to tilt the element relative to vertical;

FIG. 3 is a vertical section through the weighted detector element with the mercury switch of the present invention mounted therein;

FIG. 4 is an enlarged perspective view with parts removed for clarity of one embodiment of the mercury switch of the present invention;

FIG. 5 is an enlarged vertical section taken through the mercury switch of FIG. 4 with the switch having been tilted relative to vertical;

FIG. 6 is a diagrammatic illustration of an alarm circuit connected to the mercury switch of FIG. 4;

FIG. 7 is a side elevation of a second embodiment of the mercury switch of the present invention; and

FIG. 8 is a side elevation of the mercury switch of FIG. 7 tilted relative to vertical.

. Referring first to FIG. 1, the shoal detector system 10 of the present invention is shown supported from a boat 12 floating in a body of water with the bottom 14 of the body of water immediately adjacent to a weighted detector element 16 of the detector system. The detector element is probably best seen in FIG. 3 to include a generally cylindrically shaped container 18 having a rounded bottom, and a core 20 of lead or another heavy material so as to normally retain an orientation whereby the longitudinal axis of the cylinder extends in a vertical direction. The lead core 20 has an upwardly opening cylindrical recess 22 which is closed by a cap 24 for the cylinder threadedly or otherwise removably retained on the top of the cylinder. A rubber insert 26 is seated in a central opening in the cap 24 and has a vertical cylindrical passage therethrough adapted to receive the lower end of a hollow suspension cable 28. The suspension cable 28 is anchored at its upper end in any suitable manner to the boat 12 and the lower end has an enlarged flange 30, FIG. 3, beneath the rubber insert, preventing the cable from being pulled upwardly through the passage in the insert. To maintain a watertight seal around the cylindrical recess 22 in the lead core 20, a rubber washer, not shown, is inserted between the cap 24 and the top of the detector element 16 and the rubber insert 26 establishes a watertight seal between the cap and the suspension cable 28.

As seen in FIG. 3, the mercury switch device 30 of the present invention is seated in the recess 22 and is preferably dimensioned to fit snugly therein so as not to be jostled when the detector element 16 contacts relatively hard obstacles such as the bottom 14 of the body of water which causes the cylinder 16 to tilt relative to vertical as illustrated in FIG. 2.

A preferred embodiment of the mercury switch of the present invention is seen best in FIGS. 4 and to include a generally cylindrical glass or other suitable hollow capsule 32 with an upper end which is closed in sealed relationship with three electrodes extending downwardly into the hollow interior of the capsule 30. A lower electrode 34 of an electrically conductive wire material has a straight stem portion 40 extending vertically in a direction parallel to the central longitudinal axis of the capsule 30 and terminates at its lower end in a ring-like contact portion 42 which is circular in configuration to follow in closely spaced relationship, the contour of the inner wall of the capsule. The ringlike portion 42 lies in a plane perpendicular to the longitudinal axis of the capsule 30 and is slightly spaced from the bottom of the capsule. An upper electrode 36 of an electrically conductive wire material has a straight stem portion 44 extending downwardly in a vertical direction parallel to the central longitudinal axis of the capsule 30 and terminates at its lower end in a ring-like contact portion 46 of circular configuration which follows in closely spaced relationship the contour of the inner wall of the capsule. As with the lower electrode 34, the ring-like portion 46 lies in a plane perpendicular to the longitudinal axis of the cap sule 30 and is slightly spaced from the top of the capsule so that the ring-like contact portions 46 and 42 of the upper and lower electrodes 36 and 34 respectively are spaced from each other along the longitudinal axis of the capsule 30. A central axial electrode 38 of an electrically conductive wire material has a straight stem portion 48 extending downwardly into the capsule along the longitudinal axis of the capsule and terminates at its lower end over halfway along the length of the capsule at a location spaced above the ring-shaped portion 42 of the lower electrode 34. Each of the electrodes are connected to electrical wires which pass through the hollow interior of the suspension cable 28 and is thereby connected in an alarm circuit 50 to be described hereinafter.

A quantity of a liquid, current conducting material 52, such as mercury, is retained in the sealed capsule 30 so as not to occupy over half of the capsule but so that when the capsule is vertically oriented as shown in FIG. 4, both the lower and axial electrodes 34 and 38 respectively will be immersed therein in electrical contact with each other. The upper electrode 36, however, which is disposed adjacent the top of the capsule, is spaced from the mercury 52 when the capsule is vertically oriented and thereby is out of electrical contact with the other electrodes. When the capsule 30 is tilted relative to vertical, as shown in FIG. 5, the mercury 52 will flow into contact with the upper and lower electrodes 36 and 34 respectively placing them in electrical contact and, as will be explained later, will cause an alarm to signal displacement of the detector element 16 from its normal vertical orientation.

The alarm circuit 50 for the detector system is shown in FIG. 6 to include a power source 54 which could be a conventional DC battery having its negative terminal 56 connected to the lower electrode 34 and its positive terminal 58 connected to one terminal 60 of a single pole, single-throw on-off switch 62. The other terminal 64 of the on-off switch is connected to an alarm buzzer 66 which in turn is connected to the upper electrode 36 and to one terminal 68 of a pushbutton switch 70. The other terminal 72 of the push button switch is in turn connected to the axial electrode 38 whereby when the system is turned on by closing the on-off switch 62, the buzzer 66 can be energized either by manually depressing the push-button switch when the capsule is vertically oriented as shown in FIG. 6 so that a current passes between the lower and axial electrodes 34 and 38 respectively in energizing the buzzer or it will be automatically energized when the capsule is tilted, as shown in FIG. 5, so that the lower and upper electrodes 34 and 36 respectively are in electrical contact.

Accordingly, when the shoal detector system I0 is to be used, the detector element 16 is dropped into the water where it is suspended in a normally vertical orientation thereby retaining the mercury switch in the vertical orientation shown in FIGS. 3 and 4. In this position, the lower and axial electrodes 34 and 38 respectively, are in electrical contact so that when the on-off switch 62 is closed and the alarm system can be tested by closing the push-button switch 76 to close the circuit through the alarm buzzer 66. When the detector element 16 is caused to be angularly displaced from its normal vertical orientation as when it contacts the bottom 14 of the body of water, as shown in FIG. 2, the mercury switch 30 will be tilted, as shown in FIGv 5, so that the lower and upper electrodes 34 and 36 respectively come into electrical contact causing the alarm buzzer 66 to be energized signaling the operator of the boat that shallow water conditions exist.

It will, of course, be apparent that by varying the quantity of mercury 52 in the capsule, the sensitivity of the switch can be varied. In other words, the more mercury in the capsule the less the capsule will have to be displaced from vertical to close the alarm circuit. It should also be appreciated that regardless of the direction of tilt of the capsule 30, the mercury 52 will engage both the lower and upper electrodes 34 and 36 respectively since they are disposed in a circular ring-like manner continuously around the walls of the capsule.

If a test circuit were not desired in the shoal detector system 10, the axial electrode 36 would not be necessary and the switch device would take the form illustrated in FIGS. 7 and 8 where lower and upper electrodes 74 and 76 respectively extend through the closed top of a cylindrical glass capsule '78 or the like with the lower electrode 74 having a straight stem portion 80 extending downwardly adjacent to the longitudinal axis of the capsule to be slightly spaced from the bottom of the capsule and having a ring-like circular contact portion 82 following the contour of the inner wall of the capsule at its lower end. The upper electrode 76 also has a straight stem portion 84 extending adjacent to the longitudinal axis of the capsule and a ring-like circular contact portion 86 conforming to the contour of the inner wall of the chamber adjacent to the top of the capsule. In this embodiment, it is apparent that the switch would remain normally open until the capsule 78 were inclined as shown in FIG. 8 so that mercury 88 in the capsule would engage both elec trodes to close the switch by placing them in electrical contact and thereby energize an alarm circuit connected to the switch device.

It will be appreciated from the foregoing description that the mercury switch of the present invention is of relatively simple construction and yet is adapted to sense tilting movement in any direction. Furthermore, the switch is designed so that a third test electrode 38 can be utilized therewith, allowing a circuit connected to the switch to be tested without tilting the switch capsule.

Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example and that changes in details of structure may be made without departing from the spirit thereof.

What is claimed is:

1. A shoal detection system for suspension from a boat comprising,

a normally vertically oriented switch element having a hollow capsule, a first electrode in the capsule having a contact portion adjacent the bottom of the capsul conforming to the inner peripheral configuration of the capsule, a second electrode in the capsule having a contact portion adjacent the top of the capsule conforming to the inner peripheral configuration of the capsule, a third electrode in the capsul extending along the central vertical axis of the capsule from the top of the capsule to a location between the contact portion of said first and second electrodes, and a quantity of liquid, current-conducting material in the capsule having a depth sufficient to complete electrical contact between said first and third contacts when the capsule is vertically oriented,

cable means suspending the switch element from the boat so that it hangs freely in the water beneath the boat, and

an alarm circuit including an electrical power source,

an electrically responsive alarm element, a first onoff switch connected in series with the power source, alarm element and the first and second electrodes whereby when the first on-off switch is closed and the capsule is inclined relative to vertical so that the liquid flows into contact with both the first and second electrodes the alarm will be energized, and a second on-off switch connected in series with said power source, alarm element and the first and third electrodes whereby when the second on-off switch is closed and the capsule is vertically oriented, the alarm will be energized.

2. The shoal detection system of claim 1 wherein said switch element is mounted within a normally vertically oriented detector element near the top of the detector element and wherein the lower portion of the detector element is heavier than the switch element to encourage the detector element to remain vertically oriented when freely suspended from the boat. 

1. A shoal detection system for suspension from a boat comprising, a normally vertically oriented switch element having a hollow capsule, a first electrode in the capsule having a contact portion adjacent the bottom of the capsul conforming to the inner peripheral configuration of the capsule, a second electrode in the capsule having a contact portion adjacent the top of the capsule conforming to the inner peripheral configuration of the capsule, a third electrode in the capsul extending along the central vertical axis of the capsule from the top of the capsule to a location between the contact portion of said first and second electrodes, and a quantity of liquid, current-conducting material in the capsule having a depth sufficient to complete electrical contact between said first and third contacts when the capsule is vertically oriented, cable means suspending the switch element from the boat so that it hangs freely in the water beneath the boat, and an alarm circuit including an electrical power source, an electrically responsive alarm element, a first on-off switch connected in series with the power source, alarm element and the first and second electrodes whereby when the first on-off switch is closed and the capsule is inclined relative to vertical so that the liquid flows into contact with both the first and second electrodes the alarm will be energized, and a second on-off switch connected in series with said power source, alarm element and the first and third electrodes whereby when the second on-off switch is closed and the capsule is vertically oriented, the alarm will be energized.
 2. The shoal detection system of claim 1 wherein said switch element is mounted within a normally vertically oriented detector element near the top of the detector element and wherein the lower portion of the detector element is heavier than the switch element to encourage the detector element to remain vertically oriented when freely suspended from the boat. 